Explosion-proof low-high temperature system



March 27, 1956 R. c. WEBBER EXPLOSION-PROOF LOW-HIGH TEMPERATURE SYSTEM 3 Sheets-Sheet 1 Filed April 17, 1955 wzfw ' ATTOF/VAV.

March 27, 1956 R, c, wEBBER 2,739,453

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EXPLOSION-PROOF LOW-HIGH TEMPERATURE SYSTEM Filed April 17, 1955 3 Sheets-Sheet 5 INVEN TOR. .EGZEEFT CI M23321? United States Patent EXPLOSION-PRQOF LOW-HEGH TEMPERATURE SYSTEM Robert C. Webher, Indianapolis, ind.

Application April 17, 1953, Serial No. 349,423

Claims. (Cl. 62-4) The present invention relates to refrigeration systems and particularly to a means for controlling the temperature of the refrigerant entering the coils of the evaporator for the purpose of quickly defrosting the freezing chamber and for thereafter raising the temperature of the freezing chamber to an extremely high temperature when and where it may be desirable to do so.

The primary object of the invention is to provide an explosion proof high-low temperature system including a chamber in which extremely high or extremely low temperature can be obtained and controlled solely by means of the temperature of the refrigerant circulated through the coils of the evaporator, and to this end to provide, in such a system, means for by-passing the refrigerant, flowing from the compressor, over an electrically-energized heater element prior to its passing through the evaporator, whereby the refrigerant will conduct heat to the chamber in which the evaporator is located, instead of absorbing heat therefrom.

A still further object is to provide means for cooling the refrigerant leaving the evaporator before it is returned to the compressor to prevent overheating of the compressor during the periods the refrigerant is passing over the above-mentioned heater element.

Another object is to provide a novel construction for the above-mentioned heater means whereby the heater element can be easily removed and replaced.

Still another object is to provide, in a conventional refrigeration system, novel means for quickly and automatically defrosting the coils of the evaporator so that the temperature of the freezing chamber will not be raised any considerable amount, and to this end to provide means for automatically raising, at certain intervals, the temperature of the refrigerant flowing from the compressor to the evaporator and for maintaining this increased temperature until the temperature of the evaporator is raised above the melting point of the condensate on the evaporator coils at which time the system will be returned to its freezing cycle.

Ancillary objects will become apparent as the description proceeds.

To the accomplishment of the above and related objects, my invention may be embodied in the forms illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific constructions illustrated and described, so long as the scope of the appended claims is not violated.

Fig. 1 is a diagrammatic view of one system embodying my invention;

Fig. 2 is a longitudinal sectional view through the'heater means forming a part of my invention;

Fig. 3 is a reproduction of a visual recording of a test made with my invention illustrating one example of the degree of temperature control obtainable by the use of my invention; and

Fig. 4 is a diagrammatic view of my invention used as a quick defrosting means for a conventional refrigeration system.

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Referring more particularly to the drawings, and especially to Fig. 1, I have shown two, more or less conventional refrigeration systems modified in accordance with my invention. The first system, referred to generally by the reference numeral ill, comprises a compressor 11, conduit 12 connected to conduct compressed refrigerant from the compressor to an oil trap 13, conduit connected to conduct refrigerant from the oil trap to a condenser 15, conduit 16 connected to conduct refrigerant from the condenser to a receiver 17, conduit 18 connected to conduct refrigerant from the receiver to an expansion valve 19, preferably through a heat exchanger 18', conduit 20 connected to conduct refrigerant from the expansion valve to an evaporator referred to generally by the reference numeral 21, and conduit 22 connected to return refrigerant from the evaporator to the compressor 11, all more or less according to conventional practice.

It has been found that, by inter-connecting two such systems so as to bring the compressed refrigerant from a second compressor 26 into heat exchange relationship with the evaporator of the first system, extremely low temperatures in the region of 200 F. can thereby be obtained at the evaporator of the second system. This has proven to be a more practical method for obtaining such low temperature than that of using a single and larger compressor, since, in the illustrated system, to obtain such temperatures, the pressure in either system will seldom exceed 60 lbs./ square inch in a specific application, while pressures as high as 600 lbs./ square inch much be used in a similar application using the single compressor.

To so effect such inter-connection between the two systems, it is conventional practice to construct the evaporator of system 1b of a relatively large outer coil 24', to either end of which conduits 2i) and 22 are connected, and a smaller coil 25 threaded axially through coil 24 and connected to conduct the refrigerant of the second system 23.

The system 23 comprises a compressor 26, conduit 27 connected to conduct compressed refrigerant from the compressor to an oil separator 28, conduit 29 connected to conduct refrigerant from the oil separator to a condenser 30, conduit 31 connected to conduct refrigerant from the condenser to one end of the coil 25 of evaporator 21, preferably throgh a heat exchanger 31', conduit 32 connected to conduct refrigerant from the other end of the coil 25 to a receiver 33, conduit 34 connected to conduct refrigerant from the receiver to an expansion valve 35, conduit 36 connected to conduct refrigerant from the expansion valve to an evaporator 37 surrounding a chamber 38, and conduit 39 connected to return refrigerant from the evaporator to the compressor 26, all more or less according to conventional practice.

Systems similar to the above have been known and used heretofore to obtain and hold the interior of the chamber 38 at extremely low temperature. However, with the advent of the atomic age and with recent discoveries in the metallurgical fields, it has become desirable that some means he had whereby the temperature of a test chamber, such as chamber 38, be variable from about 200 F. to temperatures as high as +300 F. Customarily heretofore, this result has been accomplished by placing electrically energized heater elements within chamber 38. During times when the temperature is being raised, the refrigeration systems are simply shut off and the heaters energized.

The above-described system, however, has several undesirable features, one of these being the possibility of explosions Within the chamber due to the presence of the electric heaters therein. Some applications of such a device, especially in the atomic research field, make the use of such electric heating means within the chamber progreases hibitive. It is the solution of invention is primarily directed.

into the conduit 29 interconnecting receiver 28 and condenser 3d, 1 place a T-joint Heater means 41 has one end connected by conduit 42, through a fluid valve 43, and conduit 44- to the T-joint 4b. The other end of heater 41 is connected, through conduit 45, to conduit 36, whereby refrigerant can be conducted from the compressor 26 to the evaporator 37 lay-passing the condenser 30, coil of evaporator 2ft, receiver 33, and expansion valve 35.

Since the compressed refrigerant coming from compressor 26 will seek the path of least resistance, upon the opening of valve 43 refrigerant will flow from conduit 29 through conduit valve 43-, conduit 4-2, heater 41, conduit 45, conduit 36, evaporator 37 and conduit 39 back to compressor 26. Refrigerant flowing from heater 41 to evaporator 37 will be at an extremely high temperature resulting in the rapid elevation of the temperature of chamber 35.

During these heating periods of chamber 38, some of the refrigerant in the system 2? always remains in the coil 25 and i maintained at an extremely low temperature (about 40 F.) by system Closing of valve 43 will cut off the flow of refrigerant through heater 41 and return it to its path through coil 25. The extremely cold refrigerant in that coil will be immediately forced through expansion valve and through evaporator 37 to quickly lower the temperature of chamber 38.

Thus it will be seen that the temperature within chamber 38 can be changed from extremely low temperatures to relatively high temperatures merely by controlling the temperature of the refrigerant flowing through evaporator 37. No electrical heating means are needed within chamber 38 and therefore the explosion hazard from this source is entirely eliminated.

During heating cycles of the system, refrigerant flowing from evaporator 37 and returning to compressor 26 is relatively hot, so hot in fact, that to permit its return to the compressor, under some circumstances, would cause overheating of the compressor. Where this possibility exists, I prefer to provide a cooler 46 in the conduit line 39 to remove any excess heat from the returning refrigerant.

While it is possible, and sometimes desirable to opcrate valve 43 manually, I presently believe it more convenient to employ a solenoid operated valve and control the coil 47 thereof by a switch 48 placed in an accessible and convenient position for the operator.

Heater 41 is, of necessity, of large electrical capacity and the electric element thereof must be easily removable and replaceable in case of breakdown. For this reason, I prefer to construct the heater as shown in Fig. 2. A tubular member 49 is open at one end for the reception therein of an electric resistance heater element 50. Means such as the clamp 51 is provided for removably fixing the element in tube 49. Surrounding tube 49 is a jacket 52 spaced from the walls of tube The jacket is provided with an inlet port 53 in one end and an outlet port 54 in the opposite end. Refrigerant entering through port 53 from conduit 42 passes over the heated surface of tube 49 and escapes through port 54 into conduit 45. Replacing of element St in no way disturbs the closed refrigerant system, making the replacement of the element a relatively simple operation requiring little time.

To prevent overheating of heater 41 during cooling cycles of the system, I prefer to control the temperature of the refrigerant in the heater by means of the thermoresponsive switch 55.

The temperature of the evaporator 21 of system 10 I prefer to control by a Eli-Low pressure switch 56 responsive to the refrigerant pressure leaving evaporator 21. During heavy demands on the system, the pressure will be raised, actuating switch 556 to put system it) in operation. During heating cycles, the load on evaporator 21 will be at a minimum and the pressure will be low.

this problem to which my Thus system 1d will operate only enough to maintain the refrigerant in coil 25 at a predetermined temperature. In eifect, the load on evaporator 37 of system 23 controls the pressure of the refrigerant in system 10, thus controlling the periods of operation of that system.

The temperature in chamber 33 primarily controls the operation of compressor 26 in system 23 through a Hi- Low thermo-responsive switch 57 of conventional construction. Such a switch will open or close, within a given differential, to maintain a chamber at a given temperature, either hot or cold. For safety purposes, I prefer to provide a high pressure cut-elf switch 58 electrically connected in series with switch 5'? and compressor 26 so that, if, at any time, the pressure of the refrigerant leaving evaporator 37 should exceed a predetermined maximum, the compressor will be shut down.

in Fig. 3, I have reproduced a recording disc on which is recorded a visual record of one test made with the system embodying my invention. As will be seen from an inspection of this record, the temperature was maintained at approximately -1tl0 F. throughout most of a twen -four hour period. During this period, the controls were actuated several times to raise the temperature of chamber 33 to +160 F. within approximately two minutes and to return the temperature of the chamber to F. in a slightly longer time (say between 7:30 and 9:30 a. m.). in actual tests, the temperature of the chamber' can be raised from 2G8 F. to {200 F. in approximately three minutes and returned to -20? F. in approximately twenty minutes.

No other system now known to me is capable of such a wide range of temperature control without the use of electric heater elements directly within the chamber 35. My system not only gives such control but does so without the danger of explosion resulting from the presence of the electric heaters within the chamber.

In Fig. 4, I have shown my invention incorporated in a more or less conventional refrigeration system 60 modified in accordance with my concept to provide quick defrosting means for such a system.

System 61) comprises a compressor 61, conduit 62 connected to conduct compressed refrigerant from the compressor to an oil trap 63, conduit 64 connected to conduct refrigerant from the oil trap to a condenser 65, conduit 66 connected to conduct refrigerant from the condenser to a receiver 67, conduit connected to conduct refrigerant from the receiver to an expansion valve 69, preferably through a heat exchanger 70, conduit 71 connected to conduct refrigerant from the expansion valve to an evaporator '72, and conduit 73 connected to return refrigerant from the evaporator to compressor 61, all more or less according to conventional practice.

At some point in the conduit system connecting the compressor to the expansion valve 69, I provide a T-fitting '74. I presently believe the optimum position of such fitting to be in conduit 64 between oil trap 63 and condenser 65. A heater element '75, similar to element 41, is connected at one end to fitting 74 by means of conduit 76, and at the other end, by means of conduit 77, to evaporator 72. Valve means 78 is located in conduit 76 to control the flow of refrigerant through heater 75.

Upon the energization of heater and the opening of valve 78, refrigerant will flow from compressor 61 through conduit 62, oil separator 63, conduit 64, T-fitting '74, conduit 76, heater 75, conduit 77, evaporator 72, and back to the compressor through conduit 73. (In some applications I prefer to provide a cooler 73' in line 73 similar to and for the same purpose for which cooler 46 is provided.) As the refrigerant fiows through heater 75, it will be raised to a high temperature and will in turn rapidly dissipate the heat as it passes through evaporator 72 thus quickly melting away the condensate on the coils thereof. At the moment the temperature of the coils becomes suflicient to have melted all the condensate, if valve 78 is then closed, refrigerant will then flow through expansion valve 69 to the evaporator to lower the temperature thereof so that the temperature of the freezing chamber 79, in which evaporator 72 is located, will not be changed appreciably.

While this defrosting cycle can be controlled manually, I prefer to provide means for accomplishing it automatically. To this end, i provide a solenoid-operated valve 78. in order to put the defrosting system into operation at some given interval I have here provided a clock-driven switch 80 which is designed to close the contacts 81 thereof at certain given intervals, say once in each twenty-four hours. Timing devices of other types could, of course, be used in place of switch 80 such as a device which would count the number of times the door to chamber 79 was opened, closing contacts 81 after a given number of such openings. Still other types could be employed.

A three-pole relay 82 is here employed to be activated initially by the closing of contacts 81 and to be de activated by the opening of a thermo-responsive switch 83 responsive to the temperature of the coils of the evaporator '72.

The various electrical components are connected as follows: From the line a conductor 84 connects to one side of the compressor motor 85. Conductor 86 connects the other side of the motor to one contact of the conventional thermo-responsive switch 87 within chamber 79, and conductors 88 and 89 connect the other side of this switch to the line. Thus when the temperature of the chamber reaches a predetermined high, compressor 61 will be activated.

The clock motor of switch 80 is here shown as being connected to one side of the line through conductors 84. and 90, and to the other side of the line through conductors 91, 92 and 89. The motor drives a cam 93 on which rides a follower 93. The cam is so shaped that it will momentarily close contacts 81 once during each twenty-four hours.

One element of contacts 81 is connected to one side of the line through conductors 92 and 89, and the other element of the contacts 81 is connected by conductor 94 to the coil 95 of relay 82. The other side of coil 95 is connected to the other side of the line through conductors 96 and Thus when contact 81 is closed, coil 95 is energized to close the contacts of relay 82.

Since, in this instance, the contact 81 is closed only momentarily, I prefer to provide a holding circuit for coil 95 of relay S2 in the form of the normally-closed thermo-responsive switch 83. One side of the line is connected through conductor 92 to one element 97 of switch 83, and the other element 923? is connected through conductor 99 to one side of the normally open contact set 100 of relay 82. The other side of contact set 100 is connected through conductor 94 connected to coil 95. Thus, the moment contacts 81 close to energize coil 95, contact 100 is closed to establish the holding circuit in series with switch 83. This circuit will be broken to deactivate relay 82 upon the subsequent opening of switch 83 to be described later.

I prefer to provide a manually operated switch 101 connected in parallel with contacts 81 so that relay 82 can be manually activated in case of failure of clock switch 89.

The activation of relay 92 will also close contact set 102 thereof to simultaneously energize heater 75 and open valve 78. One side of contact set 102 is here shown connected to the line through conductors 84, 96 and 103. The other side is connected through a conductor 104 to heater 75, and by conductor 105 to solenoid valve 78. The other side of heater 75 is connected to the other side of the line through conductors 106 and 89. The other side of solenoid valve 78 is connected to the other side of the line through conductors 107 and 89.

A third contact set 108 is likewise closed upon activation of relay 82. This set is connected in parallel with the contacts of thermo-responsive switch 87 by means of conductor 109 connected to conductor 86, and conductor 110 connected to conductor 89, for a purpose later to become apparent.

The operation of the control circuits is as follows: At a given time, timer will momentarily close contacts 81 thereof, thereby energizing coil to close contact sets 100, 102, and 108 of relay 82. Contacts 81 will then open, but the coil 95 will remain energized through the circuit including contact set and switch 83 which is normally closed at the operating temperatures of chamber 79 but which opens when the temperature of coils 72 reaches a predetermined higher temperature.

Since compressor motor 85 is normally energized only upon the closing of switch 87, I provide the further energizing circuit for said motor through relay contact set 108. Thus the compressor will be activated upon the activation of relay 82. At the same time contact set 102. will close to energize heater 75 and open valve 78.

Refrigerant will now flow through the heater 75 and evaporator 79 quickly raising the temperature of the coils thereof to melt the condensate thereon. As soon as the temperature of the coils 72 reaches a predetermined high, the contacts 97 and 98 of switch 83 will open, thereby breaking the holding circuit for relay 82. This will close valve 78 and deenergize heater 75. If the temperature of chamber 79 has not then increased to the closing temperature for switch 87, compressor motor 85 will also be deenergized. If, however, the defrosting cycle has so raised the temperature of chamber '79, the compressor will continue to operate but, since valve 78 is now closed, refrigerant will flow through expansion valve 69 to evaporator '72 thus quickly lowering the temperature of chamber 79.

The use of my invention presents a relatively simple, trouble-free, and automatic means for doing a job heretofore done manually or much less efficiently by other means than is possible in my system.

While I have illustrated and described my invention as a high-low refrigeration system, and as a quick defrost method for refrigeration systems, there is a further use to which my basic concept can be put with advantageous results. I have not thought it necessary to specifically illustrate and describe this further use since I believe it to be apparent in the light of the prior disclosures.

The use to which I refer is that in which a refrigeration system, similar to that illustrated in Fig. 4, is used as a combination heating and air-conditioning system. The evaporator 79 is used as the room heat-exchanger, over which room air is circulated, and the condenser 65 is placed on the outside of the building. During the cooling cycle, the system operates in the conventional manner-the refrigerant flows from the compressor to the exteriorly located condenser, where it gives up heat; from there to the receiver, through the expansion valve to the evaporator, and back to the compressor. During the heating cycle, the refrigerant flows from the compressor, over the heater (similar to heater 75), through the room heat-exchanger (evaporator), by-passing the expansion valve and back to the compressor. During the heating cycle, it will be noted that the eXteriorly located condenser, such as that at 65 in Fig. 4, and the receiver are by-passed due to the location of the branch in the line which connects to the heater 75.

Such use of my invention would provide a simple, compact and highly efficient combination heating and airconditioning system, the efiiciency 'being especially high during the heating cycle since the heat generated by the compression of the refrigerant, together with the heat introduced by the heater unit, will be transferred directly to the room heat-exchanger unit.

I claim as my invention:

1. In a high-low temperature system, a first compressor, a first oil separator, conduit means connecting said first compressor to .said'first oil separator, a first condenser, a first receiver, conduit means connecting said first oil separmor to said first receiver through said first condenser, a first expansion valve, afirst evaporator comprising an outer fluid coil and an inner fiuid coil threaded through said first coil, conduit means connecting said first receiver to one of said coils through said first expansion valve, conduit means connecting said one coil to said first compressor, a second compressor, a second oil separator, conduit means connecting said second compressor to said second oil separator, a second condenser, conduit means connected to said second oil separator and dividing into two branches, one of said branches connecting to the other of said coils of said first evaporator through said second condenser, a second receiver, a second expansion valve, conduit means connecting said other coil to said second expansion valve through said second receiver, valve means, heater means, the other of said branches connecting to said heater means through said valve means, a second evaporator, conduit means connecting said heater means and said second expansion valve to said second evaporator, cooler means, and conduit means connecting said second evaporator to said second compressor through said cooler means.

2. The system of claim 1 including electrical control means for said first compressor comprising a first pressureactuated switch responsive to the pressure in said conduit connecting said one coil of said first evaporator to said first compressor, and control means for said second compressor comprising a second pressure-actuated switch responsive to the pressure in the sai conduit means connecting said second evaporator to said second compressor, and a thermo-rcsponsive switch responsive to the temperature of said second evaporator, said second pressureactuatcd switch being electrically connected in series with said thermo-responsive switch.

3. In a refrigeration system comprising a compressor, a condenser, means connected to conduct compressed refrigerant from said compressor to said condenser, a receiver, means connected to conduct refrigerant from said condenser to said receiver, an expansion valve, an evaporator, means connected to conduct refrigerant from said receiver to said evaporator through said expansion valve, means connected to return refrigerant from said evaporator to said compressor, and means responsive to the load demands on said evaporator for controlling energization of said compressor, the invention including means for defrosting said evaporator comprising electrically energized heater means, means connected to conduct refrigerant from said compressor to said evaporator through said heater means lay-passing said expansion valve, valve means connected to control the flow of refrigerant through said heater means to said evaporator, and electrical control means comprising timer means having a set of electrical contacts, electrical actuating means for said valve means, a normally closed, merino-responsive switch responsive to the temperature of said evaporator, relay means having a plurality of normaliy-open contacts, and conductor means connected to establish a plurality of circuits comprising a series circuit including one side of a power source, the coil of said relay means, the contacts of said timer means, and the other side of said power source, a hold-in. circuit for said relay including said one side of the power source, said relay coil, one set of contacts of said relay means, said thermo-responsive switch, and said other side of the power source, an energizing circuit for said heater means including one side of a power source, another set of contacts of said relay means, said heater means, and the other side of said power source, an energizing circuit for the valve actuating means comprising one side of a power source, said other set of relay contacts, said actuating means, and the other side of said power source, and a further energizing circuit for said compressor comprising a power source, the motor of said compressor, a further set of relay contacts, and the other side of said power source.

4. The device of claim 3 in which said timer means comprises an electrically driven device for opening and closing the contacts thereof.

5. The device of claim 4 including a manually-operable switch electrically connected in parallel with the contacts of said timer means.

References Cited in the file of this patent UNITED STATES PATENTS 

